Environmental life cycle assessment of wheat production using chemical fertilizer, manure compost, and biochar-amended manure compost strategies.

Using manure compost (MC) as a substitute for chemical fertilizer (CF) has been regarded as an effective strategy to promote sustainable crop production. The application of biochar in compost production could significantly mitigate the emission of gaseous pollutants and improve compost quality. However, comprehensive investigations of the environmental performance of crop production using CF, MC, and biochar-amended MC strategies are scarce. Therefore, in this study, wheat production using four fertilizer strategies, including CF, MC, and biochar-amended MC with biochar addition rates of 5% (MCB5) and 10% (MCB10), was comparatively assessed in terms of their environmental performance using the life cycle assessment (LCA) method. Compared to the CF strategy, the majority of midpoint impact categories and all assessed damage categories (except for human health and resources in MCB10) were mitigated using the compost strategies. Furthermore, as the biochar application rate increased, the biochar-amended MC strategies remarkably decreased the impacts on the global warming potential, stratospheric ozone depletion, and land use, and greatly increased the impacts on ozone formation (human health), fine particulate matter formation, and terrestrial acidification. Overall, biochar-amended MC with a biochar addition rate of 5% (MCB5) is recommended as the optimal strategy due to its relatively low environmental impact. Moreover, combined with the results of the sensitivity analysis, biogenic air pollutant emissions derived from the compost and biochar production stages were identified as the most important hotspots contributing to the undesirable environmental impacts. These findings advance our understanding of the environmental performance of wheat production using biochar-amended MC.